Early onset periodontitis is a disease characterized by a rapid progression of loss of the tooth supporting tissues in adolescents and young adults. This study was undertaken to study the pattern of progression of this disease and to identify potential risk factors. Adolescents with early onset periodontitis were identified within a population of 14,000 pupils in grades 8 to 12 examined by a national survey of the oral health of US children conducted by NIDR during the 1986/87 school year. A group of controls were matched to disease cases on gender, race, age, geographic location and metropolitan status. The cases and controls were followed over a period of 6 years during which clinical measurements were undertaken to monitor the attachment loss, caries, dental fillings, gingival inflammation and local plaque retaining factors. Subgingival plaque and blood samples were collected from these subjects, and microbiological and immunological assays were performed on the samples. The analyses are underway to assess the potential of these factors in discriminating between the cases and the controls.